The present invention relates to a power transmitting apparatus having a continuously variable transmitting function capable of greatly increasing engine efficiency as an automobile transmission. More particularly, the present invention relates to a power transmitting apparatus which utilizes a winding effect of transmitting coils with respect to a drum.
Conventionally, various power transmitting apparatuses having a gear-type transmission capable of converting revolution speed and transmitting torque of an output shaft in accordance with a load of a drive source have been used. In automobile transmissions, a gear-type transmission is normally connected to an engine through a clutch and a torque converter, and the speed of an output side is altered by changing the gear ratio.
However, in conventional power transmitting apparatuses, since speed is changed stepwisely by meshing gears, the speed change range is narrow. In order to widen the range, a large number of combinations of gears are required and, accordingly, the structure of the apparatus becomes very complicated.
For this reason, in the case of automobile transmissions, three- to four-stage speed changes are commonplace. However, with such a speed change, the engine revolution number is varied greatly whenever the speed is changed and, especially whenever the automobile is accelerated, the speed is increased from a low-speed range and thus the speed cannot be accelerated at the most efficiently revolution number, i.e., a large load is applied to the engine and much energy is lost.
In the case of a transmission using a torque converter, although a manual speed change operation is unnecessary, since a fluid pressure mainly using oil is utilized for transmitting power, power transmitting efficiency at the time of acceleration is inferior, and since most of engine output is consumed as heat even at the time of constant speed running, energy loss is great and efficiency is inferior.
The present invention has been accomplished in view of the above circumstances, and it is an object of the present invention to provide a power transmitting apparatus which has a continuously variable transmitting function of wide speed change range with a simple structure, and which is suitable as a transmission for an automobile capable of efficiently transmitting a power of a drive source.
To achieve the above object, according to the present invention, there is provided a power transmitting apparatus comprising a rotation shaft which obtains a power of a drive source and rotates in a predetermined direction, a drum fixed to an outer periphery of the rotation shaft, helical transmitting coils mounted on an outer periphery of the drum at constant clearances from one another, a driving wheel and a follower wheel rotatably provided on opposite side of the drum with the transmitting coils interposed therebetween, and a variable-speed motor for rotating the driving wheel in the same direction as the drum, in which a power of the drum is intermittently output to the follower wheel in a pulse transmitting manner through the transmitting coils by controlling a speed of the variable-speed motor, wherein each of the transmitting coils has a spring property, one ends of the transmitting coils engage the driving wheel and the other ends engage the follower wheel, when a tensile force caused by rotation of the driving wheel is applied to the one ends of the transmitting coils, the transmitting coils are wound around the outer periphery of the drum, thereby rotating the follower wheel in the same direction as the drum, the follower wheel is mounted on the rotation shaft through a one-way clutch such that the revolution number of the follower wheel does not exceed the revolution number of the drum, and when the revolution number of the follower wheel exceeds a predetermined revolution number of the drum, a centrifugal clutch for rotating the driving wheel at the same speed as the drum is provided.
Further, in the power transmitting apparatus, the driving wheel comprises annular portion for surrounding the centrifugal clutch and teeth receiving a power from the variable-speed motor, the driving wheel is connected to the variable-speed motor through a transmission system having gear meshing the teeth, and the transmission system includes excessive load-preventing means for idling the gear when the power is transmitted from the side of the driving wheel to cut off the transmission of power to the variable-speed motor.